We are moving our kitchen sink as part of kitchen remodel. The old sink drained traditionally, with a straight vent / drain line from the waste pipe in the basement to the exterior vent in the roof. I plan to use an island bow vent below the window, but the old vent line runs down to the waste line to what will be the left and upstream of the new sink drain and vent. To have it connect in the proper order, I need to know if I can disconnect the old vent from the waste line and run a horizontal pipe to the right and then down to a location forward of the new drain and vent lines. The line would run about 4 feet vertically above the waste line for about 6 feet and then come down forward of the new lines. This would position it as the last connection on the waste line before it leaves the house for the septic system. This is a one story house with cathedral ceilings, so the vertical distance from the waste line to the roof is about 20 feet. We are in Massachusetts and AAVs are not legal. Basically, I am asking if I can leapfrog the old vent line past the new lines and whether that is both functional and legal.

Thanks in advance.

Hi Sailr

Bow vents are very tricky and specific in Mass.

If you are still around and want to work through this I can help you. A drawing posted here would be invaluable to both of us, if possible!

Mark

Hi Mark,

Thanks for your response. I have attached a digram of what I am trying to work with. Everything above the sink and to the right is glass or structure to the roof line (contemporary house design). Please let me know if you have any additional questions.

Thanks again,

Sailr

What you call a "bow vent" we call a "island vent".
A few questions. Why are you installing two cleanouts to a vent line that has nothing draining into and disregarding the line that drains the sink?
I see you're connecting to a existing vent stack. According to your diagram why not simply do away with the bow vent and arm over to the vent stack from the trap? What am I missing here? The way your diagram is set up I see no reason for a bow vent.
Your vent stack looks to be close enough to tie to. What's the problem? Back to you, Tom

Here is one way of doing it. Either this way, or take the drain straight down and take the vent up just below the window and over. This is the standard everywhere that I know of. You will have to drill a couple studs, but not to worry, even if you only have 2x4 outside walls, if you drill the correct size holes, it won't bother your structural support (just make sure to center the holes, we drill 2 9/16 holes). No need for an island vent here. This is how it has been done for years, and still is, at least in my area. Our inspector prefers the method in the second pic, as long as there is a cleanout on the drain, as it eliminates the trap arm, witch makes snaking the drain easier in the future. Don't worry about the "area of concern" as this pic was posted by someone who was asking if this was okay, which it is in most areas. I would ask your inspector how he would like to see it done. Good luck and let us know what you decide.

Oh, and in the first pic, down worry about the second (left) vent, it is just for a future island sink. Of course, you don't need that.

Yeah, as pointed out by these guys, you should be able to drill through the studs to the left of the sink and use the old vent.

If for some reason you cannot do this, please explain and I will give you the correct way to plumb the bow vent in Mass. Your drawing is not correct in many ways, OK? Here, in Mass. there are 3 different ways to install a bow vent... your vent would fall under figure 13C under venting in the Mass. State code.

Mark

Hi Mark,

First, thanks again for responding and likewise to Speedball and MyGirlsDad. When I looked at Fig 13C, the primary difference I noticed was the vent taking a right hand turn to the stack and not a left (since mine happens to be on the left). I also had the stack vent line in my drawing continuing down to the drain line, which I was told elsewhere was a deviation from the UPC, but required in MA. However, it is not shown in the Fig13c drawing. I did not have the clean out in the drain line in my drawing, which was an oversight in my drawing, but it would definitely be there. (My understanding on clean outs is that more is better than less.) The figure 13C drawing is actually easier to implement.

I have an integrity question with regard to going through the studs. When originally built, there were several studs under the window (more than required - guessing the builder thought more was better?) the drain line ran outside the wall through a cupboard. Our configuration won't allow the line to stay outside the wall, so it would have to go back into the wall. However, based on how close the studs are, it would require multiple joints to get the drain line from the stack to the sink drain (6 or 7 joints over 4 - 5 feet). That seems like a recipe for failure - more joints, more potential for failure, all of which are hidden from view in the wall. My thought was that this alternative was less risky, since there would be longer continuous runs, fewer joints, and all would be visible. Am I over concerned about the multiple joints in the wall?

Thanks,

Sailr

it would require multiple joints to get the drain line from the stack to the sink drain (6 or 7 joints over 4 - 5 feet) Ever hear of notching the studs?
Have you checked this job with your inspector? If not now would be a mighty fine time. Cheers, Tom

If I notch the studs I ruin the structural integrity of the wall, which is why one would normally run a hole saw through the center, as Mark stated (per code). Considering it is 14' at it's highest point and supporting large windows, that's not such a great idea.

Hi Sailr

First, I would check with the inspector and see if you can drill holes through the stud and connect to the existing vent. Structurally, if drilled, you should be fine. In terms of number of joints in the wall you could remove one stud (or notch and sister a new stud on when finished) so you could shove 30" pieces through and you could use sch. 40 PVC PRESSURE COUPLINGS (joints are twice as deep) and that should guarantee no leaks (as well as testing this).

If none of that floats your boat (or the inspectors) and you still decide you want to install the bow vent then you want to stay directly with figure 13C exactly as drawn except for going left as you said (and adding the cleanouts). You DO NOT want to connect the vent as shown in your drawing...not a MASS. code and has nothing to do with UPC here, OK? Check out Fig. 13C below...straight forward for your application.

I will be surprised if any inspector in Mass. will allow you to bow vent instead of go through the studs. Bow vents are usually only allowed under special circumstances, although 14 feet tall wall may be a "special exception", maybe?

Let us know more, OK?

Mark

Hi Mark,

Again, many thanks for your assistance and the professionalism in your answers. It's funny, I have gotten a lot of flack attempting to understand this and do the right thing and told by many on various sites to just hire a plumber (which my budget prohibits at this point, due to multiple issues we have had to tackle at once - new electrical panel, roof leaks, HVAC, etc). Ironically, I have received numerous pieces of conflicting and incorrect guidance from people who are said to be professionals (one never actually knows on a forum for sure) and knowledgeable on Mass codes and practices. As the saying goes, you get what you pay for.

I like the suggestion on drilling the holes in new studs and sistering them against the notched studs to retain the structural integrity of the wall. Oddly enough, you are the first to suggest what is ultimately a simple solution to the integrity issues with the wall and ultimately gets us to the standard and preferred vent installation. Using the pressure couplings would provide further piece of mind, even though fewer would be necessary using this strategy for the structure.

Best regards,

Sailr

I'm for notching the studs,
9.23.5.4.[1] TOP PLATES IN WALLS SHALL NOT BE NOTCHED,DRILLED OR OTHERWISE WEAKEND TO REDUCE THE UNDAMAGED WIDTH TO LESS THAN 50mm [2"] UNLESS THE WEAKENED PLATES ARE SUITABLY REINFORCED. This reinforcing can be a metal stud plate or simply fur out the stud. In any case, notching the studs makes more sense then installing a bow vent. Good luck. Tom

Thanks for popping back in and sharing your thoughts Salir... glad if we helped!

Mark

After reading this, glad AAV's are acceptable in Georgia!

You said it, Brian! You should see my customers' faces when they want to add a sink somewhere in the middle of the house and I start trying to explain why it will cost THOUSANDS of dollars just to rip-out/repair the ceiling areas and fish this VENT PIPE that they really don't even understand (and really have no interest in knowing) through half the darn house!

It gets even better when I start explaining the code required ventilation fan... LOL!

Estimates can be really funny sometimes!

Mark